Thermostatic switch



Nov. 17, 1936. E. w. EVANS THERMOSTATIC SWITCH Filed 0011 34 H w i N- Evans I tatented Nova 17, itidd FA'EENT @FFWE tfldlsilt E'EEEMQSTA'MC SWITCH Ernest W. Evans, Viecennes, 1nd.

Application illctohes i 3 Claims.

This inventionrelates to an improved thermo= static switch for incubators and While being particularly designed to be employed in connection with the structure shown in my co-pending app1l- 5 cation for vaporizing mechanism for incubators filed January 29, 1934, Serial No. 788,396 is, never timeless, well adapted for general use.

A salient object of the invention is to provide a thermostatic switch which will be more or less sensitive and thus adapted to maintain the tem= perature of an incuoatoi relatively constant.

A further object of the invention is to provide a switch wherein out slight expansion of the thermostatic element employed will be suficient to open the switch and similarly, wherein hut slight contraction of said element will permit the switch to again he closed.

Another object of the invention in this ccn= nection is to provide a switch wherein the mer 'cury tuoe employed will be mounted on a rocker movable to shift the tube from either side oi the pivotal center of the vocker to the other to effect opening and closing of the switch and wherein the expansive movement of the thermo static element will be transmitted through a level in such a Way that but a relatively slight ex= pension of said element will serve to swing the lever and actuate the rocker.

And the invention seeks, as a still further cl9= ject, to provide a switch which is dependable so that no fear need be entertained of overheating the incubatcif, which may be set to filllCtlOll any desired vtei"onerature and which will eliminate arcing.

Othet iecidental objects of the invention tloh.

Figure 2 is a detail sectional view on the lilo 2--2 of l.

li igate 3 is detail sectional viev, OK! the 3 d of it Figure l is a fragmentary perseective View ticularly showing the lugs employed on the free end of the rocker actuating lever, and

Figure 5 is a fragmentary side elevation show ing a slightly modified form of the invention.

In carrying the invention into effect, 1 employ a rectangular frame embodying side eats it con nected by end cars it and respectively. e end bar it is continued to provide lateral 1158 it at the rear corners oi the frame and these lugs are apei'tured to acconnncdate loclts or lost. serial No, ('Jl. ace-sic) like for securing the device against the inner face of a wall of an incubator, such a well being con= ventionally illustrated at M.

Formed on the end bar it of the frame is a hearing it and screwed through said bearing is an adjusting screw it. As will be observed, the screw it extends freely through the wall it of the incubator and l'emovably fixed to the cute? end of said screw is an appropriate handle ill. Formed on the end bar iii of the frame is a hear ing it and slidalc-le freely through said heating is a plunger is aligning with the screw Removably mounted hetween the inner ends of the screw it and plunger it) is a thermostatic Git.

ment 26;. This thermostatic element may he c? any. appropriate character but preferably com arises spaced pairs oi expansihle waters, as shown, connected axially to provide unit and projecting item the front and rear wafers are studs 29 which are accommodated in suitable sockets in the inner ends of the plunger and screw for sup porting the thermostatic element therehetwee" Formed on the frame at one oi the forward cor 21ers thereof is a iorwardly projecting yoke 22 ex-= tending in a plane with the frame and pivoted between the sides of said yoke is a channel shaped.

socket 255%, preferably of sheet metal.

triangular shaped side M which, as

drought out in Figure 8 are more or less snugly t received between the sides of the yoke 22 d through said flanges gocrting the rocket a pivot gain freely aitp= l movement.

tending transverse n the flanges 9 the all relation thereto s1" flanges.

Formed on the c i erogecting il slia teo the and is. a laterally project cg parallel relatio;

thus extends in facet of the plunger it so that "I.

the plunger will ccact therewith and is reduced in width toward free end to provide a terminal 32 extending beneath the yoke 22 at a ii l'lt angle thereto. Formed on the terminal o lever. as particularly seen in Figm'e l, is a of upstanding lugs 33 which, as brought out in Figure 2, straddle the pin '26 of the rocker 23. Thus, as will be seen, when the le er 29 is swung, the rocker will be actuated.

Screwed into the forward side of the lever 29 near its lower end is a stud34 aligning with the plunger l9 and extending through the terminal 28 of the arm 21 is an adjusting screw 35 aligning with said stud and provided with a collar 36. Fitting at one end over the stud 34 is a spring 31 resting at its opposite end against said collar so that, as will be seen, the screw 35 may be adjusted for tensioning said spring. The spring 31 will, of course, tend to swing the lever toward the frame and extending through the free end portion of the leveris an adjustable stop screw 38 to coact with the end bar i2 of the frame for limiting the lever in its movement under the influence of said spring.

Attached by screws or otherwise removably fixed to the rocker 23 is a mercury tube holder 39 having spaced pairs of upstanding spring fingers 40 and removably clamped between said fingers is a mercu'rytube 4| containing a drop more or less of mercury 42. Extending into the tube at the forward end thereof are spaced terminals 43 and connected to said terminals are circuit wires 44. Mounted upon the side bars III of the frame, but insulated therefrom, as seen in Figure 1-, are binding posts 45 to which the wires 44 are attached so that the switch may thus, as will be appreciated, be easily connected in the circuit of an electric heater for the incubator.

When the switch is closed, the rocker 23 stands in the full line position shown in Figure 2 so that the mercury tube 4| is thus tilted downwardly at its forward end. Accordingly, the drop of mercury 42 will contact the terminals 43 to close the circuit therebetween. When the thermostatic element 20 expands, however, the plunger 9 will be shifted forwardly to rock the lever 29 against the tension of the spring 31. The lever 29 will thus be caused to swing the rocker 23 from the full line position of Figure 2 to the dotted line position shown. Accordingly, the mercury tube 4| will be tilted downwardly'at its rear end so that the drop of mercury 42 will collect in the rear end of the tube, thereby breaking the circuit between the terminals 43.

As the thermostatic element 20 subsequently contracts, the spring 31 will, of course, act on the lever 29 for returning the lever to its initial position, so that the lever will be caused to swing the rocker 23 and return the mercury tube 4| to a position tilted downwardly at its forward end, when the drop of mercury 42 will again close the circuit through the terminals 43. The switch will thus function automatically and, of course, the tension of the spring 39 may be regulated by adjusting the screw 35. As the screw It forms an abutment for the thermostatic element 20, this screw provides a means, as will be readily appreciated, for varying the temperature at which the lever 29 is swung for actuating the rocker 23 and opening the switch and, of course, the screw may be readily adjusted at the exterior of the incubator.

Attention is now directed to the fact that only a slight movement of the lever 29 is required to swing the free end of the lever across the pivotal center of the rocker 23. Furthermore, as the plunger l9 coacts with the lever near the pivoted end thereof, a correspondingly slight forward movement of said plunger is required to swing the lever. As a result, only a slight expansion of the thermostatic element is required to open the switch, thus making the switch sensitive and highly responsive to changes in temperature within the incubator. Furthermore, as the pin 26 is located close to the pivot pin 25 of the rocker, movement of the lever 29 will cause the free end thereof to quickly swing the rocker from either side of the pivotal center thereof to the other with a correspondingly quick making and breaking of the circuit.

In Figure 5 of the drawing, I have shown a slight modification of the invention. In this modification, the frame 46 is mounted in a vertical plane. This frame is identical with the frame previously described with the exception that the frame 43 is provided at its upper forward corner with an upstanding yoke 41. Pivoted between the sides of said yoke is a rocker 49 like the rocker 23 and which carries a tube holder 49 like the tube holder 39. Carried by the tube holder 49 is a mercury tube 50 like the tube 4|.

The rocker 43 is equipped with a pin 5| like the pin 26 and coacting with said pin is a lever 52 like the lever 29 with the exception that the lever 52 is provided at its free end with a hook 53 which engages over the pin 5|. In thus employing a hook at the free end of the lever 52, the use of a stop screw on said lever like the screw 38 is rendered unnecessary, the hook being adapted'to coact with the pin 5| for limiting the lever in its movement toward the frame. Otherwise, this modification of the invention is identical with the construction previously described and as it functions in like manner, further description is believed unnecessary.

Having thus described the invention, I claim:

1. A thermostatic switch including a frame, a rocker pivoted thereon, means mounted on the rocker and movable thereby for making and breaking a circuit, a pivoted lever coacting at its free end with the rocker for actuating the rocker, a plunger supported by the frame and coacting with the lever near the pivot point thereof, a screw carried by the frame, a thermostatic element mounted between and supported by said screw and plunger and expansible for swinging the lever in one direction, and yieldable means for swinging the lever in the opposite direction, said screw being adjustable for varying the temperature at which the rocker is actuated by said lever under the influence of said element.

2. A thermostatic switch including a frame having a yoke thereon, a channel shaped rocker pivoted between the sides of said yoke, a pin carried by the rocker adjacent the pivot point thereof, an arm projecting'from the frame, a lever pivoted upon said arm and at its free end engaging said pin for swinging the rocker from either side of its pivotal center to the other, means mounted on the rocker and movable thereby for making and breaking a circuit, a plunger slidable through the frame to coact with the lever near the pivot point thereof, a screw carried by the frame in alignment with said plunger, a thermostatic element mounted on the screw and plunger therebetween and expansible for swinging the lever in one direction, a screw adjustable on said arm, and a spring interposed between the latter screw and said lever and operable for swinging the lever in the opposite direction, 'said first mentioned screw being adjustable for varying the temperature at which the lever is swung under the influence of said element.

3. A thermostatic switch including a frame, a,

. rocker pivoted thereon, means mounted on the rocker and movable thereby for making and breaking a circuit, a pivoted lever for actuating the rocker, a plunger slidable in the frame to enact with the rocker, ascrew carried by the frame in alignment with the plunger, a thermostatic element supported by said screw and plunger therebetween and. expansible for reclaing the lever in one direction, and a. spring coacting with the lever in alignment with the plunger for swinging the lever in the opposite direction.

ERNEST W. EVANS. 

